Lesson: Chapter 7 — Quantification of Elements and Compounds

7.1. Relative atomic mass 10 of 12 Reset answers

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Question 10

The mass of a potassium atom is 6.476 × 10^-23 g and that of a carbon-12 atom is 1.99 × 10^-23 g. What is the relative atomic mass of potassium?

A 468 B 3.25 C 39 D 0.31

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39. A_r = (6.476 × 10^-23) ÷ (1/12 × 1.99 × 10^-23) = 39.

3.25 comes from dividing by the whole mass of the carbon atom, forgetting the twelfth. 468 is 39 × 12, from applying the 12 twice.

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